A fiber reinforced composite is widely used as a light-weight structural material. As a reinforced base material for the fiber reinforced composite, there is a fiber laminate. The fiber reinforced composite is formed by impregnating matrix resin into the fiber laminate. The fiber reinforced composite is used as structural materials of rockets, airplanes, automobiles, ships, and buildings. There is also a fiber reinforced composite configured by changing the thickness according to a shape in use.
As shown in FIG. 7, a fiber laminate 80 disclosed in Patent Document 1 is configured by stacking a plurality of sheet-shaped reinforced fibers 81. The fiber laminate 80 includes a base 82, an intermediate section 83, and a surface layer section 84. In the base 82, the sheet-shaped reinforced fibers 81 are stacked to have a uniform thickness. In the intermediate section 83, the sheet-shaped reinforced fibers 81 are stacked with the ends of the sheet-shaped reinforced fibers 81 shifted stepwise. The surface layer section 84 covers the entire surfaces of the base 82 and the intermediate section 83. The thickness of the fiber laminate 80 is gradually changed by shifting the ends of the sheet-shaped reinforced fibers 81 in the intermediate section 83.
Patent Document 2 discloses a fiber laminate including fiber layers in which short fibers (discontinuous fibers) are oriented in a predetermined direction in order to improve the shape-imparting properties to a complicated structure such as a curved surface structure of the fiber laminate and cause the fiber laminate to exhibit the strength in the predetermined direction.
However, if the thickness of the fiber laminate is continuously changed as disclosed in Patent Document 1 in the fiber laminate including the fiber layers in which the discontinuous fibers are oriented in the predetermined direction, a problem described below occurs. That is, when the fiber layers are stacked with ends of the fiber layers shifted, in a portion where the thickness of the fiber laminate continuously changes, the number of stacked layers of the fiber layers is different depending on the position in the layer direction. Therefore, each time the thickness of the fiber laminate changes near the ends of the fiber layers, the orientation of the discontinuous fibers changes and the physical properties of the fiber laminate vary.